LIDOCAINE HYDROCHLORIDE VISCOUS
Clinical safety rating: safe
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
Lidocaine is a local anesthetic that stabilizes neuronal membranes by blocking voltage-gated sodium channels, thereby inhibiting the initiation and propagation of action potentials. It also has antiarrhythmic properties (Class Ib) by accelerating repolarization and reducing automaticity in cardiac tissues.
| Metabolism | Primarily hepatic via CYP1A2 and CYP3A4 to monoethylglycinexylidide and glycinexylidide; also conjugated to 4-hydroxy-2,6-dimethylaniline. |
| Excretion | Renal: ~90% as metabolites (mainly 4-hydroxy-2,6-xylidine and glucuronides), <10% unchanged. Biliary/fecal: minor (<5%). |
| Half-life | Terminal elimination half-life: 1.5–2 hours (adults); prolonged in heart failure (2.5–4 hours) or hepatic disease (up to 5–7 hours). Context: short t1/2 limits toxic accumulation with topical use. |
| Protein binding | ~70% bound to alpha-1-acid glycoprotein (AAG) and albumin; binding increases with AAG elevation (e.g., inflammation). |
| Volume of Distribution | 1.1–2.0 L/kg (adults). Clinical meaning: extensive distribution into well-perfused tissues, including brain and heart, contributing to potential CNS/cardiac toxicity. |
| Bioavailability | Viscous topical (oral mucosa): approximately 3–15% (highly variable due to swallowing and mucosal absorption; significant first-pass metabolism). Not bioavailable orally (IV form only for systemic use). |
| Onset of Action | Viscous topical (oral mucosa): 1–2 minutes; infiltration: 2–5 minutes; no parenteral IV formulation for viscous product. |
| Duration of Action | Viscous topical: 30–60 minutes (mucosal anesthesia); infiltration: 1–2 hours (with epinephrine). Viscous use indicated for pharyngeal anesthesia. |
Adult: 15 mL (300 mg) orally every 3 hours, not to exceed 8 doses in 24 hours. Viscous formulation swished and swallowed.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment due to potential accumulation of metabolites. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 50%. Child-Pugh Class C: Avoid use or reduce dose by 75% with close monitoring. |
| Pediatric use | Weight-based: 4.5 mg/kg/dose (maximum 300 mg) orally every 3 hours as needed; not to exceed 4 doses in 12 hours. Safety in infants <6 months not established. |
| Geriatric use | Reduce initial dose by 25-50% due to decreased hepatic clearance; monitor for CNS toxicity and cardiac effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Beta-blockers may increase the risk of lidocaine toxicity Can cause CNS toxicity (seizures) and cardiovascular collapse.
| FDA category | Animal |
| Breastfeeding | Lidocaine is excreted into breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.4-0.6. The relative infant dose is estimated to be less than 2% of the maternal weight-adjusted dose, which is considered clinically insignificant. Therefore, lidocaine viscous is generally compatible with breastfeeding. However, caution is advised if the infant has hepatic impairment or is premature. Monitor the infant for signs of local anesthesia (e.g., difficulty sucking, numbness of mouth). |
■ FDA Black Box Warning
Contains lidocaine, which can cause methemoglobinemia, particularly in neonates and infants. Use with extreme caution in patients with G6PD deficiency, or concurrent use of oxidizing agents. Risk of systemic toxicity (seizures, cardiac arrest) if absorbed in large amounts.
| Common Effects | ventricular arrhythmias |
| Serious Effects |
Hypersensitivity to lidocaine or any amide-type local anesthetics; history of methemoglobinemia; application to large areas of denuded or inflamed tissue; severe hypotension or heart block (for systemic use).
| Precautions | Systemic absorption can cause CNS stimulation/depression, cardiovascular depression, and methemoglobinemia. Use smallest effective amount. Avoid application to traumatized mucosa or open wounds. Monitor for signs of toxicity in young children and elderly. Discontinue if rash or irritation occurs. |
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| Teratogenic Risk |
| Lidocaine hydrochloride viscous is classified as FDA Pregnancy Category B. Animal reproduction studies have not demonstrated fetal risk, and there are no adequate and well-controlled studies in pregnant women. However, lidocaine can cross the placental barrier by passive diffusion. At term, fetal/maternal plasma concentration ratio is approximately 0.5-0.7. No teratogenic effects have been reported in humans when used appropriately. However, high systemic levels can cause fetal bradycardia and acidosis. Use during first trimester is generally considered low risk, but caution is advised. During second and third trimesters, risk remains low but monitor for maternal toxicity. |
| Fetal Monitoring | Maternal monitoring includes assessment for lidocaine toxicity (CNS effects like lightheadedness, perioral numbness, metallic taste, tinnitus; cardiovascular effects like hypotension, bradycardia). Fetal monitoring should include fetal heart rate assessment for bradycardia or late decelerations, particularly with high doses or prolonged use. If administered near term, monitor for neonatal depression (respiratory, CNS). No specific routine fetal monitoring is required for topical use, but systemic absorption should be minimized. |
| Fertility Effects | Lidocaine has no known direct effects on fertility in humans. Animal studies have not shown impaired fertility at clinically relevant doses. However, severe systemic toxicity could theoretically affect reproductive function, but at therapeutic topical doses, no impact on fertility is expected. |